1. Field of the Invention
Embodiments of the invention relate to methods for synchronizing clocks in a communication network as well as to a corresponding communication network.
2. Background of the Related Art
Clock synchronization is the basis for the proper functioning of different processes in communication networks, e.g. automation networks and cellular communication networks. In such networks, a first network element provides a first clock as a master clock and other second network elements using second clocks synchronize their clocks with the first clock.
There are several standards for clock synchronization, e.g. the standard IEEE 1588 (IEEE=Institute of Electronics and Electrical Engineers). In known synchronization standards, first messages in the form of sync messages are transmitted from the first network element to the second network elements and second messages in the form of line delay requests are transmitted from the second network elements to the first network element. The exchanged messages include time stamps of the first clock of the first network element as well as of the second clocks of the second network elements. Based on those messages, the line delay between the first network element and the second network elements can be calculated and a synchronization of the second clocks in the second network elements with the first clock of the first element can be performed.
Known synchronization methods work well unless there are delays caused by further network elements between the first network element and the second network elements, said further network elements not being part of the synchronization process. This is because those intermediate network elements may cause arbitrary delays, e.g. due to congestion, not enabling a correct calculation of the line delay between the first network element and the respective second network elements.